It's not being so long since we've entered public beta, but time could be needed for this matter.
Even if Stack Exchange team have designers, proposing your ideas have chances to help and influence them for our theme creation.
So, don't be shy! Show or tell what you think would be a great logo and design for our site!
I suggest publishing one design by answer so that we, the community, can vote on it. But don't hesitate to create more than one if you feel inspired!